Method of producing copy



United States Patent 3,096,711 METHOD OF PRODUCING COPY Wilhelm Ritzerfeld, Franzensbader Str. 21, Berlin- Dahlem, Germany, and Gerhard Ritzerfeld, Schoriemer Allee 14, Berlin-Grunewald, Germany No Drawing. Filed Apr. 14, 1959, Ser. No. 806,382 Claims priority, application Germany Apr. 19, 1953 Claims. (Cl. fill-149.4)

The present invention relates to a method of producing copy and, more particularly, the invention is concerned with a duplicating process for producing a multiplicity of copies from a transfer sheet, such as a hectographic process.

' According to a preferred manner of carrying out the present invention, the image on the transfer sheet is produced photographically, however, the present method lends itself also to the copying of typed images and the like.

It has been proposed to incorporate one of the components for forming the transfer dye into the transfer sheet, and to include the other component in the liquid which is applied during the transfer of the image from the transfer sheet to a copy sheet. It has also been proposed to form a relief image in a :gelatine layer containing silver halides and a non-coloring dye component. The other dye component was then supplied in the form of an alkaline or acidic liquid included in the copying liquid applied to transfer sheet and copy sheet in the duplicating machine.

All of these prior art methods are connected with the very serious disadvantage that the duplicating machine as well as conduits and pumps for the copying liquid had to be made of alkali and acid resistant materials in order to withstand the attack of the copying liquid. This created difliculties in the designing and construction of the duplicating machinery and also increased their cost. Actually, all structural elements which possibly might come in contact with the corrosive copying liquid, such as copying drum and bearing, in fact the entire apparatus would have to be built of corrosion resistant materials in order to overcome this disadvantage.

Since practically all commercially available duplicating machines fail to provide corrosion resistant moistening and liquid conveying devices, it was not possible to operate the same in accordance with the above discussed proposed methods.

It is therefore an object of the present invention to provide a simple and economical duplicating method which will not subject the duplicating machinery to corrosive attack.

It is another object of the present invention to provide an effective method of producing a great number of copies from an image produced on a transfer sheet, in a simple and economical manner.

l It is a further object of the present invention to produce an image on a transfer sheet which may be transformed into a transferable dye image prior to introduction of the transfer sheet into the duplicating machine and to operate the duplicating machine with substantially neutral liquids, thus avoiding corrosive damage.

Gther objects and advantages of the present invention will become apparent from a further reading of the description and of the appended claims.

With the above and other objects in view, the present invention broadly comprises in a method of producing copy the steps of forming on a transfer sheet an image consisting of the leuco compound of a dye, reacting the leuco compound on the transfer sheet with a substance adapted to transform the same into a dye soluble in a substantially neutral solvent, so as to obtain on the transfer sheet an image consisting of the soluble dye, and transferring the image in the presence of a substantially neutral solvent for the dye from the transfer sheet to a copy sheet.

According to one preferred manner of carrying out the method of the present invention, copy is produced by carrying out in the indicated sequence, the steps of forming on a carrier sheet a layer consisting essentially of gelatine having distributed therethrough a silver halide, the leuco compound of a dye and a substantially colorless oxidizing agent adapted in the presence of an acid to transform the leuco compound into a soluble dye, the carrier sheet and the gelatine layer jointly forming a transfer sheet, photographically forming a relief image in the gelatine layer, reacting the leuco compound of the relief image with an acid adapted to transform the same into a dye soluble in a substantially neutral solvent selected from the group consisting of water and lower molecular monoand polyvalent liquid alcohols and mixtures of the same, so as to obtain on the transfer sheet an image consisting of the soluble dye, and transferring a surface layer of the image in the presence of the substantially neutral solvent for the dye from the transfer sheet to a copy sheet.

The method of the present invention also includes the forming on at least one face of a carrier sheet a layer consisting essentially of at least one substance selected from the group consisting of fats and Waxes, the substance having evenly distributed therethrough the leuco compound of a dye and an oxidizing agent of low color intensity adapted in the presence of an acid to transform the leuco compound into a soluble dye, transferring image forming portions of the layer onto a transfer sheet so as to form on the transfer sheet an image consisting of portions of the layer, reacting the leuco compound of the image with an acid adapted to transform the same into a dye soluble in a substantially neutral solvent, so as to obtain on the transfer sheet an image consisting of the soluble dye, and transferring the image in the presence of a substantially neutral solvent for the dye from. the transfer sheet to a copy sheet.

In certain cases, it has been found advantageous to form the soluble dye image by forming on a carrier sheet a layer consisting essentially of a Water soluble binding agent having distributed therethrough a Water soluble acid in solid state, moistening the layer so as to dissolve a portion of the binding agent and of the acid, contacting a face of a transfer sheet having on the face an image consisting of the leuco compound of a dye with the moistened layer so as to react the dissolved acid with the leuco compound transforming the same into a dye soluble in a substantially neutral solvent selected from the group consisting of water and lower alcohols, thereby obtaining on the transfer sheet an image consisting of the soluble dye.

Thus, according to the present invention, the leuco compounds forming the image which is to be copied are transformed by reaction with liquid, solid or gaseous acids into the colored water and/ or alcohol soluble corresponding dyes. Duplicating is subsequently carried out by contacting the transfer sheet carrying the dye image in a duplicating machine wherein the copy sheet, which has been moistened with a dye dissolving non-corrosive liquid, is placed in contact with the image carrying transfer sheet.

The term leuco compound is to be understood to comprise broadly such colorless or slightly colored compounds which either by reaction with acids alone or by reaction with acids and oxidation can be transformed into strongly colored water/ and or alcohol soluble dyes, such as the lactone of crystal violet, spiro-dibenZo-pyrane or spiro-dina-phtho pyrane.

When it is desired to use leuco compounds of triphenyl methane dyes, the same are also subjected to oxidation either simultaneously with being reacted with the acid or before or after the acidification.

When it is desired to duplicate photographic images in accordance with the present invention, transfer sheets are used which are formed with a gelatine layer into which the silver halides and the leuco compound of a dye have been incorporated. The thus formed photosensitive layer is then exposed in conventional manner, and by hardening development of the gelatine layer and washing away of the non-hardened gelatine portion, a positive mirror relief of gelatine containing the leuco compound is formed and serves as transfer layer. The leuco compounds are transformed, prior to duplicating, into the transfer dyes by being exposed to acid in liquid, solid or gaseous state. When required, the gelatine layer may contain, in addition to the silver halide and the leuco compound, also a colorless or slightly colored oxidizing agent.

The image which is to be duplicated, particularly if the same consists of types or the like, may also be produced by placing a carrier sheet covered with a mixture of suitable fast and/ or waxes having distributed therethrough the leuco compound and the oxidizing agent, behind the transfer sheet and transferring portions of the mixture from the carrier sheet to the transfer sheet by writing or typing, etc. on the free face of the transfer sheet. The thus obtained print image consisting of colorless or only slightly colored leuco compounds and oxidizing agents in the wax or fatty mixture is then subjected to acid applied either in liquid, solid or gaseous form, and thereby transformed into a colored alcohol and/ or water soluble dye. Reference is made herein to the application of acid in solid form. As will become apparent from a further reading of the specification, when the acid is supplied in solid form, there is also present a suitable liquid, i.e. a liquid in which the acid is soluble, in a quantity sufficient to provide for the desired reaction between the acid and the leuco compound.

As described further above, the leuco compound of the print image can be transformed into its strongly colored alcohol and/or water soluble dye, by being exposed to acid fumes, and if necessary by being subjected in addition thereto to an oxidizing reaction prior to transfer of portions of the image to a plurality of copy sheets.

It is also within the scope of the present invention to introduce the acid in solid form, for instance embedded in a water soluble binder substance consisting for instance of suitable colloids, methylcellulose, gum arabic, or the like. The binder substance containing the acid forms a layer on a carrier sheet and the thus formed layer is then brought in contact with the image carrying face of the transfer sheet. Thereby, the layer on the carrier sheet is to be moistened with a liquid in which acid and binder substance are soluble, or the layer of the carrier sheet is pressed upon a still moist transfer sheet so that the moisture of the transfer sheet suifices to dissolve a portion of the acid and the binder material.

It is also possible to incorporate in the binder material an oxidizing agent in solid but potentially soluble form into the binder material, in addition to the solid but soluble acid.

Low molecular alcohols such as methanol or ethanol, water or mixtures of water and alcohol, which may also include polyvalent or somewhat higher molecular alcohols in order to increase the solvent action, are used as substantially neutral copying liquids.

Broadly, any volatile acid whet-her organic or inorganic may be used for transforming the leuco compound into the corresponding dye. However, it has been found particularly advantageous to use vapors of formic acid for this purpose.

Various modifications of the present invention can be carried out, for instance, sections only of a transfer sheet made according to the present invention may be copied, with the help of a neutral copying liquid, onto copy sheets; or, sections only of the leuco compound image on the transfer sheet may be treated with acid so as to form the transferable colored dye. In the latter case, it is possible to first produce copies of only a portion of the total image on the transfer sheet, namely, of the portion only which has been acid treated, and subsequently to treat additional portions of the transfer sheet with acid and to produce copies of the entire image or of large portions of the image which has been formed originally in leuco compound form on the transfer sheet.

It is also possible to transform the leuco compounds of the image prior to introducing of the transfer sheet into the duplicating machine, into colored alcohol and/or Water soluble dyes, by treating the leuco compounds containing face of the transfer sheet with solutions of hydroxyca-rboxylic acids.

Advantageously, aqueous solutions of hydroxycar- 'boxylic acids having a concentration of at least 5% are employed. Excellent results were obtained with 25% solutions of hydroxycarboxylic acids, whereby glycolic acid has been found to be most suitable from a technical as well as from a physiological point of view. However, 'very good results were also obtained with lactic acid. Relatively small quantities of formic acid, for instance about 4% are advantageously added to the aqueous solution of hydroxycarboxylic acids such as a 25% solution of glycolic acid.

The transformation of the leuco compounds into soluble dyes can also be carried out by treating the image forming leuco compounds on the transfer sheet with solutions of acetic acid. Preferably aqueous solutions containing at least 10% acetic acid and most preferably about 15% acetic acid are used. Again, the addition of formic acid in quantities such as 4% has been found desirable.

It is also possible to produce the soluble dye by treating the leuco compound with formic acid solutions in the manner described above with respect to other acids. Preferably aqueous solutions containing at least 3% and most preferably about 5% formic acid are used.

Broadly, it is also possible to use according to the pres ent invention substances of acidic reaction provided the same are capable to transform the basic dye-forming compound into a water insoluble dye which however is soluble in organic solvents, particularly alcohol, in order to transform the image on the transfer sheet into a soluble colored dye prior to introduction of the transfer sheet into the duplicating apparatus.

The following acidic compounds belong to the group of compounds which may be used for this purpose:

a. saturated aqueous solutions of substituted phenols, for instance nitrated phenols such as p-nitrophenol or picric acid; or

b. saturated aqueous solutions of substituted aromatic carboxylic acids such as salicyclic acid; or

c. saturated aqueous solutions of substituted naphthols,

such as a-nitronaphthol.

Example I A printing form or transfer sheet having a gelatin layer containing silver halides and the leuco compound of methyl violet or malachite green is exposed in a reflex photocopy device. When using a positive original, the light sensitive printing form has been previously exposed to ultraviolet light and image forming exposure is carried out with a light source containing a large amount of yellow whereby at the portions of the gelatin layer which are exposed to yellow light, the efiect of the previous ultraviolet exposure is neutralized due to the Herschel efiect, while the portions of the gelatin layer which are not exposed to a yellow light, i.e. the portions corresponding to the image which is being copied, will retain the effect of the ultraviolet exposure.

The exposed printing form is then developed in a hardening developer so that the image carrying portions of the gelatin layer will be hardened while the image-free portions of the gelatin layer can be removed with an aqueous solution.

A suitable developer has the following composition:

Water cm. 100 Pyrocatechin -g 15 Sodium sultite g 1.5 Potassium carbonate g 60 Water cm. 1000 Potassium permanganate .:g.. 30 Potassium bichromate g 30 However, since the above described oxidizing solution will cause a staining of the printing form and also might come in contact with the hands of the operator causing discoloration, it is frequently preferred to use instead an oxidizing solution containing organic peroxides, for instance benzoyl peroxide.

The oxidizing treatment will transform the leuco base of methyl violet or malachite green into the actual dye base of methyl violet or malachite green.

The oxidizing treatment lasts for about between 15 to 20 seconds.

Thereafter, the printing form is subjected to concentrated formic acid vapors for about one minute, preferably in a closed vessel.

The formic acid treatment develops the dye base to the actual dye, i.e. to methyl violet or rnalcahite green which is easily soluble in water or alcohol.

Thereafter, the printing form is attached to the printing drum of the duplicating machine and contacted thereon with successive copy sheets. A neutral copying liquid is used thereby for slowly dissolving surface layers of the dye image which thus are transferred to the copy sheet.

Example I] When the method of the present invention is to be used in connection with a printing form or transfer sheet on which an image has been formed by writing, typing, or the like, i.e. in a non-photographic manner, the leuco base of the methyl violet or malachite green and the oxidizing agent will be incorporated in the fat and/or wax layer of an auxiliary transfer sheet (non-coloring latent dye sheet). The non-coloring auxiliary transfer sheet is then placed with its fat or wax layer in contact with one face of the printing torm. Upon writing or typing onto the other face of the printing form, a mirror image consisting of the fat or wax layer will be formed on the first named face of the printing form which is in contact with the auxiliary transfer sheet.

The thus produced printing form or transfer sheet is then exposed to vapors of formic acid which also may contain a small amount of acetone. The acid vapors will first trigger the oxidizing reaction between the oxidizing agent and the leuco base and they will furthermore transto rm the dye base formed by the oxidizing reaction into the colored dye.

The thus completed transfer sheet or printing form is then copied in a duplicating machine onto copy sheets which are moistened with a neutral copying liquid such as alcohol or water capable of dissolving successive surface layers of the dye image.

The composition of the active layer on the auxiliary transfer sheet may be as follows:

The barium peroxide may be replaced by other organic or inorganic oxidizing agents, for instance potassium bichromate or sodium peroxide.

As described further above, it is also possible to use an auxiliary transfer sheet for supplying the acid and/or the oxidizing agent to the leuco compound. This auxiliary sheet may be formed, for instance, with a layer containing sul-famic acid and manganese dioxide dispersed in a natural colloid such as gum arabic. The manganese dioxide can be replaced by other oxidizing oxides such as lead dioxide, and the gum ar-abic maybe replaced by other suitable carrier substances such as polyvinyl alcohols or methyl cellulose. An aqueous liquid is to be used to moisten either the auxiliary acidifying or oxidizing sheet or the printing form contacting the same.

Example 111 Water cm. 1000 Pyrocatechine g 12.5 Sodium sulfite g 0.5 Potassium carbonate g 65 Prior to use, the developer is diluted with three times its own volume of water.

During development, the black image forming portions of the mirror image are hardened, while the remainder of the gelatin will start to swell. The swelling nonhardened gelatin is removed by immersion of the formin warm water so that a mirror positive of the original consisting of leuco base containing hardened gelatin will remain. The printing form while still moist, is then immersed for 15 seconds in a 1% aqueous potassium permanganate solution whereby the leuco base of the malachite green is oxidized to the dye base. The dye base cannot be used for copying but has to be subjected to the subsequent acidic treatment in order to be transformed, prior to copying, into the actual dye salt. Accordingly, the printing form, after completion of the oxidizing treatment, is immersed for 20-30 minutes into a saturated, i.e. about 1.5% aqueous solution of p-nitrophenol. The thus produced dye is substantially insoluble in water or at least is insoluble in water to such a degree that bleeding of the dye from the relief printing image will not occur. The residual acidic solution adhering to the printing form is pressed 01f. The printing form is now fixed to the drum of a conventional duplicating machine and copies are produced with the help of a neutral copying liquid such as ethyl alcohol, in which the water insoluble dye is soluble. In this manner, it is possible to produce more than satisfactory copies from one printing form.

Example IV The printing form is exposed, developed and oxidized The acidic bath has the Water cm. 1000 p-Nitrophenol g 15 Glycolic acid 3.6% cm. 90

The oxidized printing form is immersed into the above described acidic base for between 20-30 seconds and then further treated as described in Example III.

Example V The printing form is exposed, developed and oxidized as described in Example III. The acidic bath has the following composition:

Water cm. 1000 p-Nitrophenol g 15 Concentrated chemically pure hydrochloric acid cm.

Treating time is between 15 and 20 seconds, further processing is carried out as described in Example 111.

Example VI Exposure, development and oxidation are carried out as described in Example III. Acidic treatment is carried out for 5 to minutes in a concentrated aqueous solution of salicylic acid. Further processing is carried out as described in Example III.

Example VII The printing form which has been exposed, developed and oxidized as described in Example III, is then pressed for about /2 minute against an auxiliary transfer sheet, whereby either the printing form or the auxiliary tran fer sheet has been well moistened with water prior to pressing the same against each other.

The auxiliary transfer sheet is produced as follows:

A solution of the composition described below is applied to an absorbent paper sheet having a smooth surface until the paper is saturated. The solution is prepared by dissolving 5 g. methyl cellulose in 150 cm. distilled water and adding 10 g. sulfamic acid. The thus treated paper sheet is then dried at 40 C.

After thus contacting the printing form with the auxiliary transfer sheet, the printing form is ready for copying and, with alcohol as printing liquid, about 100 good copies can be made in a duplicating machine. Should it be found that the copies obtain prematurely a blueish tinge, the treatment of the printing form with the moist auxiliary transfer sheet is to be repeated prior to continuing copymg.

Example VIII A printing formexposed and developed as described in Example III, is pressed for /2 hour against an auxiliary transfer sheet. Either the printing form or the transfer sheet must be well moistened.

The auxiliary transfer sheet is prepared as follows:

A solution of 10 g. gum arabic, 10 g. sulfamic acid and 80 cm. distilled water is prepared and g. of manganese dioxide are suspended therein. An absorbent paper sheet having a smooth surface is then treated with this solution to saturation and subsequently dried at a temperature of 30 C.

Example IX A printing form is exposed and developed as described in Example III and is then treated for seconds With a 2% aqueous potassium bichromate solution in order to oxidize the leuco compound to the dye base. Thereafter, the printing form is moistened by means of a rubber roller with an aqueous lactic acid solution to which 1.5% of u-nitronaphthol have been added. The thus oxidized and acidified printing form is installed in an alcohol duplicator and copied, using a mixture of 80 .parts by volume of ethanol and 20 parts by volume of distilled water as copying liquid. In this manner about 100 good copies are obtained.

Example X A printing form which has been produced, developed and oxidized as described in Example III, is treated for about 15 seconds with an aqueous solution containing 15% acetic acid and 1.5% p-nitrophenol. The thus treated printing form is ready for copying and about 100 good copies are obtained from the same in a duplicating machine using as copying liquid a mixture of parts by volume ethanol, 15 parts by volume distilled water and 5 parts by volume butanol.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A method of producing cop-y, comprising, in the indicated sequence, the steps of printing on a transfer sheet an image consisting essentially of the leuco compound of a dye; oxidizing substantially all of said leuco compound; reacting said oxidized leuco compound on said transfer sheet with an acidic solution so as to substantially completely transform said oxidized leuco compound into a dye soluble in water and alcoholic solvents, said solution containing a substituted phenol which renders said dye insoluble in Water without impairing the solubility of said dye in alcoholic solvents; and transferring the image formed by said dye in the presence of an alcoholic solvent from said transfer sheet onto a copy sheet.

2. A method of producing copy, comprising, in the indicated sequence, the steps of photomechanically forming on a transfer sheet an image consisting essentially of the leuco compound of a dye; oxidizing substantially all of said leuco compound; reacting said oxidized leuco compound on said transfer sheet with an acidic solution so as to substantially completely transform said oxidized leuco compound into a dye soluble in water and alcoholic solvents, said solution containing a substituted phenol which renders said dye insoluble in water without impairing the solubility of said dye in alcoholic solvents; and transferring the image formed by said dye in the presence of an alcoholic solvent from said transfer sheet onto a copy sheet.

3. A method of producing copy, comprising, in the indicated sequence, the steps of forming on a transfer sheet an image consisting essentially of the leuco compound of a dye; oxidizing substantially all of said leuco compound, reacting said oxidized leuco compound on said transfer sheet with an inorganic acidic solution so as to transform substantially all of said oxidized leuco compound into a dye soluble in water and alcoholic solvents, said solution containing a substituted phenol which renders said dye insoluble in water without impairing the solubility of said dye in alcoholic solvents; and transferring the image formed by said dye in the presence of an alcoholic solvent from said transfer sheet onto a copy sheet.

4. A method of producing copy, comprising, in the indicated sequence, the steps of forming on a transfer sheet an image consisting essentially of the leuco compound of a dye; oxidizing substantially all of said leuco compound; reacting said oxidized leuco compound on said transfer sheet with an organic iacidic solution so as to transform substantially all of said oxidized leuco compound into a dye soluble in Water and alcoholic solvents, said solution containing a substituted phenol which renders said dye insoluble in water without impairing the solubility of said dye in alcoholic solvents; and transferring the image formed by said dye in the presence of an alcoholic solvent therefor from said transfer sheet onto a copy sheet.

5. A method of producing copy, comprising, in the indicated sequence, the steps of forming on a transfer sheet an image consisting essentially of the leuco compound of a dye; oxidizing substantially all of said leuco compound; reacting said oxidized leuco compound on said transfer sheet with an acidic solution so as to substantially completely transform said oxidized leuco compound into a dye soluble in Water and alcoholic solvents, said solution containing a substituted phenol which renders said dye insoluble in water without impairing the solubility of said dye in alcoholic solvents; and transferring the image formed by said dye in the presence of Ian alcoholic solvent therefor from said transfer sheet onto a copy sheet.

6. A method of producing copy, comprising, in the indicated sequence, the steps of forming on a transfer sheet an image consisting essentially of the leuco compound of a dye; oxidizing substantially all of said leuco compound; reacting said oxidized leuco compound on said transfer sheet with an acidic solution so as to transform substantially all of said oxidized leuco compound into a dye soluble in water and alcoholic solvents, said solution containing a substituted phenol which renders said dye insoluble in Water without impairing the solubility of said dye in alcoholic solvents; and transferring the image formed by said dye in the presence of a lower alcohol as solvent for said dye from said transfer sheet onto a copy sheet.

7. A method of producing copy, comprising, in the indicated sequence, the steps of forming on a transfer sheet an image consisting essentially of the leuco compound of a dye; oxidizing substantially all of said leuco compound; reacting said oxidized leuco compound on said transfer sheet with an acidic solution so as to substantially completely tnansform said oxidized leuco compound into a dye soluble in water and alcoholic solvents, said solution containing a nitrated phenol which renders said dye insoluble in Water without impairing the solubility of said dye in alcoholic solvents; and transferring the image formed by said dye in the presence of an alcoholic solvent therefor from said transfer sheet onto a copy sheet.

8. A method of producing copy, comprising, in the indicated sequence, the steps of forming on a transfer sheet an image consisting essentially of the leuco cornpound of a dye; oxidizing substantially all of said leuco compound; reacting said oxidized leuco compound on said transfer sheet with an acidic solution so as to transform substantially all of said oxidized leuco compound into a dye soluble in water and alcoholic solvents, said solution containing a substituted phenol selected from the group consisting of picric acid and paranitrophenol as a substance which renders said dye insoluble in water without impairing the solubility of said dye in alcoholic solvents; and transferring the image formed by said dye in the presence of an alcoholic solvent therefor from said transfer sheet onto a copy sheet.

9. A method of producing copy, comprising, in the indicated sequence, the steps of forming on a transfer sheet an image consisting esesntially of the leuco compound of a dye selected from the group consisting of the leuco compounds of triphenyl methylviolet and malachite green; oxidizing substantially all of said leuco compound; reacting said oxidized leuco compound on said transfer sheet with an acidic solution so as to transform substantially all of said oxidized leuco compound into a dye soluble in Water and alcoholic solvents, said solution containing a substituted phenol selected from the group consisting of picric acid and paranitrophenol as a substance which renders said dye insoluble in water Without impairing the solubility of said dye in alcoholic solvents; and transferring the image formed by said dye in the presence of an alcoholic solvent from said transfer sheet onto a copy sheet.

10. A method of producing copy, comprising, in the indicated sequence, the steps of forming on a transfer sheet an image consisting essentially of the leuco compound of a triphenyl methane dye; oxidizing substantially all of said leuco compound; reacting said oxidized leuco compound on said transfer sheet with an acidic solution so as to substantially completely transform said oxidized leuco compound into a dye soluble in water and alcoholic solvents, said solution containing a substituted phenol which renders said dye insoluble in Water without impairing the solubility of said dye in organic solvents; and transferring the image formed by said dye in the presence of an alcoholic sol-vent therefor from said transfer sheet onto a copy sheet.

References Cited in the file of this patent UNITED STATES PATENTS 976,417 Weiler Nov. 20, 1910 1,661,568 French et al. Mar. 6, 1928 2,040,075 Brower May 12, 1936 2,146,976 Neidich Feb. 4, 1939 2,555,603 Ogilvie June 5, 1951 2,634,677 Klimkowski et al. Apr. 14, 1953 2,755,200 Balon et al. July 17, 1956 2,935,938 OSullivan May 10, 1960 FOREIGN PATENTS 451,190 Great Britain July 31, 1936 OTHER REFERENCES Karrer: Organic Chemistry, 4th English ed., 1950, Elsevier Pub. Co. Inc., N.Y., page 449. 

5. A METHOD OF PRODUCING COPY, COMPRISING, IN THE INDICATED SEQUENCE, THE STEPS OF FORMING ON A TRANSFER SHEET AN IMAGE CONSISTING ESSENTIALLY OF THE LEUCO COMPOUND OF A DYE; OXIDIZING SUBSTANTIALLY ALL OF SAID LEUCO COMPOUND; REACTING SAID OXIDIZED LEUCO COMPOUND ON SAID TRANSFER SHEET WITH AN ACIDIC SOLUTION SO AS TO SUBSTANTIALLY COMPLETELY TRANSFORM SAID OXIDIZED LEUCO COMPOUND INTO A DYE SOLUBLE IN WATER AND ALCOHOLIC SOLVENTS, SAID SOLUTION CONTAINING A SUBSTITUTED PHENOL WHICH RENDERS SAID DYE INSOLUBLE IN WATER WITHOUT IMPAIRING THE SOLUBILITY OF SAID DYE IN ALCOHOLIC SOLVENTS, AND TRANSFERRING THE IMAGE FORMED BY SAID DYE IN THE PRESENCE OF AN ALCOHOLIC SOLVENT THEREFOR FROM SAID TRANSFER SHEET ONTO A COPY SHEET. 